Valve mechanism



Patented June 4, 1946 Wilfred A. Eaton, Elyria,

Ohio, assignor to Bendix-Westinghouse Automotive Air Brake Company, Elyria, ware Ohio, a corporation of Dela-1 Application February 17, 1944, Serial No. 522,825

11 Claims. (01. 303.54)

This invention relatesto valve mechanism and more particularly to valve mechanism for controllingthe actuators of a fluid pressure brake system.

It has previousl been proposed to employ valve mechanisms of the so-called self-lapping type for controlling the actuators of a fluid pressure brake system; such valve mechanisms being generally of the type having inlet and exhaust valves, together with means for controlling the operation of these valves including an element responsiveto the pressure supplied to the actuators thereof and a manually operated resilient element actuated by the operator, and commonly known as a graduating spring. In order to prevent the trapping of fluid pressure in the brake actuators on release operation of the brake valve, it has been necessary in the past to so arrange the parts of the self-lapping valve as to maintain the exhaust valve in open position with the brakes released, and this has necessitated sufiicient movement of the brake pedal by the operator to close the exhaust valve before any fluid could be supplied to the actuators by the valve mechanism in order to apply the brakes. While the delay necessitated by this operation has been slight, it has been sufficient in some cases to seriously delay the application of the brakes during an emergency, and

it is accordingly an object of the present inven tion to'provide, simple and efficient means for overcoming this difliculty. r

Another object of the invention is to provide control valve means of the self-lapping type so constituted as to insure a substantially instantaneous application of fluid pressure to the brake actuators.

at its upper end with the A further object of the invention is to provide,

in connection with a brake valve of the self-lapping type, auxiliary valve means controlled by the actuating pedal of the self-lapping valve for insuring a supply of fluid pressure to the brake actuators as soon as the brake pedal is operated,

Still another object of the invention is to provide, in connection with a valve mechanism of the above type wherein the exhaust valve of the self-lapping valve is normally maintained in release operation of A further object of the invention is to provide valve mechanism of the above type so constituted as to automatically supply a predetermined pressure offiuid t t gpere nq t b a p dal.

0 the brake actuators onjini ,the limits of the invention,

These and other objects and novel features of the invention will appear more fully hereinafter from the following detailed description when taken inconnection with the accompanying drawing,- whereinone embodiment of the invention is illustrated. c

It is to be expressly understood, however, that the drawing is employed for purposes of illustration'only and is not designed as a definition of reference being had for this purpose to the appended claims.

Referring to thedrawing, the invention i illustratedas including a casing 4 provided with an inlet chamber 5,anoutlet chamber 6, a diaphragm chamber 1 and an atmospheric chamber 8, the latter chamber being connected with atmosphere by means of an exhaust conduit 9. The inlet and outlet chambers are separated by means of a ported-partition Ill provided with an inlet port .1 I This port is adapted to be closed by means of an inlet valve [2 urged it toward closed position by means of a valve spring l3 interposed betweenthe upper side of the partition l0 and the lower side of'an exhaust valve 14 connected withthe inlet valve by means of a valve stem Hi. The outlet chamber: 6 is connected with a suitable'brake actuator lt'bymeans of a conduit H. In order that the operation of the inlet and exhaust valves may be suitably controlled, a valve operating element I8 is slidably mounted in a bore I9 formed in the casing and substantially in alignment with the stem of the inlet and exhaust valves, and the element I8 is provided with a bore 20 adapted at its lowere'nd to engage the upper surface of the exhaust exhaust chamber 8. Acuation for this valveelement I8 is accomplished in onedirection by means of a diaphragm 2i clamped in the casing asshown and subjected on its lower surface to the pressure in the diaphragm chamber 1, an means of a manually operated graduating spring 22 mountedfin a bore 23'for'med in the upper end of the casing, and adapted on compression to impart downward movement to the diaphragm and valve operating element; The diaphragm is thus subjected onits upper surface to atmospherlc pressure in the chamber 8, and on its lower surface to the pressure in the outlet chamber 5 .by virtue of arestricted passage 24 leading from the-outlet chamber to the diaphragm chamber 1. Operation of the grad plished by meansof Ia plunger '25 slidably mounted in the upper portion of the casing and provided witha shoulder 25, adapted for engagement valve l4 and connected d in the other direction by uating spring is acc0m-- l2 in open position as shown. In order to prevent undue distortion of the diaphragm under the ac-, tion of the spring 22, a stop 28 is provided on' the casing which serves to engage a flange 29 on the valve operating element in order to limit .down-,. Ward movement of the element. A brake pedal.

23a serves to control the operation of the plunger 25, the pedal being pivotally mounted on a bracket portion 30 of the housing by means of a suitable pivot pin 3|, and being adapted on move- T r.

ment in a counterclockwise direction to depress the plunger 25 in order to further COmpIess the graduating spring. 1 V

The elementary fluid pressure brake system shown in the drawing is further provided with a fluid pressure supply reservoir 32 having a supply conduit 33 connected to a suitable source of fluid pressure, such as a compressor, not shown, and since the inlet valve I2 is normally maintained in open position, it will be apparent that auxiliary means must be provided in order to prevent fluid pressure from being supplied to the brake actuator it when the brake pedal is in released position. Such uxiliary means includes a second inlet chamber 34 formed in the casing and connected with the supply reservoir 32 by means of a conduit 35. An auxiliary outlet chamber 36 is also providedin the casing and separated from the inlet chamber by means of a ported partition 31. Communication between these inlet and outlet chambers through the ported partition is normally prevented by means of an inlet valve 38 normally maintained in the position shown by means of a valve spring 39 inposed between the upper surface oi. the partition and the lowersurface of a secondary exhaust valve 40 carried on the upper endof a valve stem 4| which is connected at its lower end. to

the inlet valve 38. The outlet chamber 36, is connected with the primary inlet chamber 5. by

means of a suitable passage 42, and since the inlet chamber 34 is connected with the reservoir the element 43 is effected by means of a plunger 48 slidably mounted on the upper portion of the casing and in substantial alignment with the valve operating element 43, the upper end of the plunger being provided with a roller or cam follower 49 adapted to engage the surface of a quick lift cam 50-formed on the hub of the brake pedal 29a. A keyway 5| provided on the plunger is engaged by means of a suitable screw 52 carried by the casing in order to maintain the roller 49 in .alignment with the surface of the cam.

The force necessary to impart downward move- 4 ment .to the valve operating element 43 is relaby means of a conduiti35, it will be understood 5' that on opening movement of the inlet valve 38,

fluid pressure will be supplied to the primary inlet chamber 5 through the conduit 35, inlet chamber 34, ported partition 31, auxiliary outlet ohamber 36 and passage 42. Control of the operation of the inlet and exhaust valves 38 and 40 is accomplished by means of a secondary valve operating element 43 slidably mounted in the casing as shown, and provided with a bore 44 which is i adapted at its lower end to engage the upper surface of the exhaust valve 40 on downward movement of the element. The bore is connectedto an exhaust chamber by means of ports 48 formed in the wall of thebore and the exhaust chamber is connected to atmosphere by. means of an exhaust conduit. Thus-with; the parts in the position shown, communication is permitted between the outlet chamber 36 and atmosphere, while on downward movement of the valve operating element 43, communication is prevented between the outlet chamber and atmosphere and is permitted between the inlet'chamber 34 and the outletchamber 36. Downward movementof tively small due to the fact that the area of the of the exhaust valve 40 and opening of the inlet valve 38 with a very small: angular movement of the pedal 29a, in a counterclockwise direction about the pivot 3|. Assumingthat the parts'of. the control valve are in the position shown,- and .3

that the operator is desirous of effecting a slight brake application in order to check thespeed of i the vehicle, it is only necessary to move the brake pedal 254a.v downward a small amount, whereuponthe cam acts to move the plunger 48 and thevalve, operating element 43 downward to contact the exhaust valve 40 to preventcommunication between the outlet chamber 36 and atmosphere,

and to open the inlet valve 38 in order to permit communication between the inlet chamber v.34 and the outlet chamber 36, the cam 50 being so constituted that during further movement of the brake pedal to effect a further. application of the brakes, the exhaust valve 40 remainsinclosed position and the inlet valve 38 remains inopen position, The outlet chamber 36 is connected with the primary inlet chamber 5 through the passage 42, and since the inlet valve I2 is normally in open position, fluid under pressure from the reservoir 32 is immediately supplied to the brake actuator i6 through the conduit 35,.inlet chamber 34, ported partition 31, outlet chamber 3'8, passage 42, primary inlet chamberi, port ll,

primary outlet chamber 6 and conduit 11, the fluid pressure thus supplied likewise being sup-" plied to, the diaphragm. chamber 1 through the restricted passage 24. During initial operation of the pedal to close the exhaust valve 40 and open: the inlet valve 38, the graduating spring 22 willbe further compressed to a slight :degree, and if the pedal is moved sufficiently to fully open the inlet valve 38, and is then maintained in that position, the primary valve operating element i8 will be moved upward to permit closing of the inlet valve l2 when the pressure supplied to the actuator and .to'the diaphragm chamber 1 exerts sufficient force on the diaphragm to overcome the initial compression of the graduating spring 7 plus the additional compression imparted there to on operation of the pedal tomove the inlet valve 38 to open position. Whenthis action occurs, the valves l2 and [4 will be in lapped position andtthe pressure of fluid in the actuator will automatically be maintained at a value determined by the degree of compression of the graduating sprin as is well-known to those skilled in the art, it being noted that the operationof the primary self-lapping valve mechanism is'sub stantially identical to that set forth in the patent to William J. Andres and Roy S. Sanford, No.

2,133,275 dated October 18, 1938. During further'ff operation of the pedal in 'a' downwarddirection to 5: increase .the pressure of fluid supplied to these-- tuator, the inlet chamber 5 will beat all times connected'with the supply reservoir 32 in View ofiztheiconstrutcion of the cam 50 whichserves to'maintainsthe. inlet valve 38 in open position during this type of operation, and the selflapping portion of the valve mechanism will consequently operate in the conventional manner. to supply a pressure tothe actuator which increases substantially in proportion to thedegree'of further.movementtofuthe. brake pedal. Likewise, after-a .complete brake application, subsequent release movementiof thelbrake pedallwillicause fluid pressuretoibe exhausted fIOm ithB' outlet chamber-fisthrough the bore-20, andthence to atmospherexthrough chamber 8 and conduit 9 in the conventional. manner until such :timenas the pedalis'moved to complete released position; When" this position is I reached; however,-v a slight tensionrflwillcbe' maintained on the graduating spring-as heretoforellexplained, and there will consequently be atendency'sfor fluid'pressure to be trapped in :thewoutlet chamberand in,theiactuator having a. value proportional to; the degree of compression-moi the? graduating spring. :In ordentox:v insure the complete exhaust ofzfiuid pressure from the outlet: chamber filer from the actuator 16,-: means are provided..for connecting thejcutletchamber 6 with theoutletchamberiifiof.- the auxiliaryl'portion of the controlvalve, such means ;constitut ing a passage 53 connected with thechamber fipapassagel-i l connectedwith the chamber 36-and-axball check valve-55 in engagement with .the right end of the passage 53 for the purpose of permitting the flow of fluid pressure from the chamber 6 to. chamber 36 and for pre venting the flow of fluid pressure in thereverse direction-.1 It. will be understood that it is necessaryrto provide the:check valve 55in order to prevent the now of fluid vpressure from the outlet chamber .36 to theoutlet chamber 6 throughthe passagesfi lan'd 53 in view of the fact that when the valveisoperatedto apply the brakes,-the chambe'n 36His1atall times'at reservoir pressure, and the application \ofsuch a-pressure to the chamber 6 through the abovepassages-instead ofunder the control of the primary inlet valve 12 woul-d in creasethe. pressure in the :outlet chamber 6 and innthe diaphragm chamber! to a valueabove that forcwhich the graduating-spring was set,

with a resultant continuousexhaust of fluid pres sure to atmosphere from-the chamber 6 through the bore 2|];rthe exhaust chamber 8 and the exhaust conduit 9. :Thus the check valve 55effectively prevents the supplying of reservoir pressure i to chamber 6 through the passages 53 and Eb and atcthe same time permits the unrestricted exhaust of pressure from the chamber 6 through the c'hamber 36 when the-brake pedal is in 'released position and the valve operating element 431*fis movedupwardjto "operr the auxiliary ex-' Consequently when the pedalis movedto' fully released position; the pressure in the chamber 36 will force the valve operating 65y exhaust valve 40 in order to permit communica harsh rave:

element upward and out of enga'gement with the h s?! bs w e c a e far amq p ae thrb'ugh the path already de cribed, 'ancanynuia pressure which might otherwise be trapped in the outlet chamber 6 an d in the actuator. It; will flow directly to the chamber 36 throughpase st t ch ek val e. and P a 5 a duwi l a zh u eda qatmospb ret hrou h ebo All y 6 complete releasesofnthe vehicle brakesion re lease ofwthe brake pedal; ml l I LlIhus a construction, has been; provided where'- in the lnlet valve of. theself-lapping type brake valve isnormallymaintained in open position in order to provide an unrestrictedpassage for the flow of fluidrto-the brake actuator, and the construction is such that movement of the. brake pedal to elfect a brake application immediately increases the-tension on the graduating spring With a.;resultant tendency to maintain the. inlet valve-.inopen position during downward move-1 mentof the pedal.;. aiAtthe same time, initial movement .of ithe :1 pedal eto apply the brakes :results in an immediate operation of the auxiliary inlet valve :38 in: orderto' provider-a direct and unrestrictedepassagei from the supply reservoir to the inlet chamber 5, with the result thatfluid pressure is supplied to the actuator withrthe utmost rapidity. While: previous constructions have been iproposedcwherein the brake pedal was provided with a quick :lift cam operating direct- 1y .on the self-lapping valve plunger in order to insure immediate closingnofwthe exhaust valve and opening l'of the::inlet .valve, the forces involved in such aconstru'etion due to the necessity of movingtthel diaphragm downward against fluid pressure in order to operate-the valves, are so great as to renderinitial operation of th pedal towclose :the'exhausti-valve and open the inlet valve; difl'l'cult for the operator: With this type oftconst ruction, a relatively large force is required foriinitial-operationof the pedal, and since this force:fal1s-ofi rapidly-as soon-as the cam has ceased to act, there i is a tendency for the operator to suddenly depress the pedal to its full extent with a resultant severe' application of the brakeswhich is detrimental toithe' vehicle as well asedangerouslto the'passeng'ers carried therein. This difllculty is avoided in the present construction. due to the ease with which the auxiliary valve operating element 43 maybe moved down-- wardvto closet-he auxiliary exhaust valve and open..the iauxiliaryintake valve, and this con-= struction.'likewisewplaces no: restriction on the establishment of a proper-mechanical advantage betwieenthe pedal 29a and the self-lapping valve plunger -25,:,for the purpose of permitting the most satisfactory type of operation of the selflapping portion. of.,the' valve mechanism. Means are also provided for adjusting I the initial tenslonof the graduating spring 22, such means in the present'instanceabeinglillustrated as including a 1 shim 56: interposed between the shoulder 21 and the flanged portion of the plunger 25, In

likemanner, shims 51 :maybe interposed between. the plunger- U48. and the valve operating element:

43 in order tovadjust thedegreeuofiopening of the exhaust valve 40,: it :being expressly understoodshowever, that any, suitable adjusting means may be incorporated in: the mechanism 1 in plac'e of theshimsmbove' described:

.There has thus been illustrated and described in connection with the and eflicientself lapping valve-means seconstitu te'd a's -to efiect -an extremely rapid initial application 'of"'the brakesgand so constituted as to insure complete -'='re lease of fluidpressure from the brake actuators on'movementof thebrake pedal to release'd position. The -regular'inlet valve ofthe self-lapping valve' mechanism is} normally maintained-in Wideopenuposition, and fluid pressure is supplied to this valve from the reservoir by :meanstofi aniaux-il-iary inlet waive which may. l mits-4'6" and exhaustcbnduitiifl thus insuring. a, be* in-arrangedv to; ioperate :al-most; instantaneously present invention, novel on initialdownward movement of the ..-brake pedal. Thus extremely rapid application of the brakes is obtained, and at the same. time fluid pressure is initiallysupplied to the brak'e'actuators in response to an extremely small movement of 'thebrake pedalfrom released'positlon. In addition to the foregoing, theadvantages of the so-called preloading of the graduatingspringare obtained. V r I Althoughone embodiment of the present invention has been illustrated anddescribedlherein with considerable particularity, it is to be-ex-. pressly understood that variations, changes" and substitutions may be made thereinwithoutideparting: from the spirit oi. the-inventiona Reference will," therefore, be had;- tol the appended 7 claims fora definitionof the limits; of the in-.

ventionr What is claimed is: 1 1 i l. In-combination with a fluid pressureiactuatoigiself-lappingvalve means for controlling the flow of fluid to and from the motor including in: let and 'exhause valves, actuating meanstorrsaid valves including a; pressure responsive member;

and a'graduating spring, meansfor adjusting said graduating spring to maintain the inlet valve in open position until a predetermined,ipressure. is supplied to the actuator, and: a'control element having a release position and movable for increasing the compression of said spring for operating the valves to supply fluid itO said actuator, at pressures greater than .said. predetermined.-

pressure, a source of fluid pressure, and auxiliary valve means operableon initial movementzof'said control element for establishing a connection'between said source 'and self-lapping: valve means and for maintaining said connection during further movement of said element, and operable when said control element is in release position to connect said motor with atmosphere.

r 2. In combination'with a fluid pressure actua-L tonself-lappingvalve means for controlling the flow of fluid to and. from the actuator including inlet and exhaustvalves,*actuating means for said valves including a pressure responsive memher and a graduating spring, means for adjusting saidgraduatingspring to maintain the inlet valve in open position until a predetermined pressure is supplied to the actuator, anda control element having a release'positionzand operable from release position for increasing thecompression of said spring for operating said valves to supply fluid to said'actuator at pressures great-- or than said predeterminedpressure, a source'of fluid pressure, and means for controlling the sup-i plyof fluid to said actuatorthrough saidse'lflapping valve, means includingeauxiliaryfivalve means controlled by the operation Y of-=said ele-' ment for exhausting fluid from said actuator when said elementis in releaseposition-andior establishing and maintaininga connection be-- tween said source and self-lappingr valvelmeans on movement of the elementifromrelease. position. w J

3. The combination with a self-lapping valve mechanism including inlet and exhaust valves,

inlet and outlet chambers, an element-for oper-= ating the valves, means including a member. re-. sponsive to the pressure in the outlet chamber for moving the element in ,one directiom and means for moving the element in the othendirec tion including a manually operable member have, me a; release position 1 and. resilientymeans con-- necting'said manually operable member: and. element adapted to position thezelement'to closeithe exhaust valve and open the inlet valve when the manually operable member is in release position, of. means-for controlling the supply of fluid pressure to said self-lapping valve mechanism including auxiliary inlet and exhaust valves; and means controlled by movement of the manually operable member for closing the auxiliary exhaust valvev and maintaining the auxiliary inlet valve in open position to supply fluid pressure to said inlet chamber whenever said manually operable member is moved from release position.

t 41. The combination with a self-lapping valve mechanism including inlet and exhaust valves, inlet'and outlet chambers, an. element for operating the valves, means including a memberre-- ponsive to the pressure in the outlet. chamber tor moving ;the element in one direction, and means for moving thezelem'ent in the other direction including a manually operable memberuh'avingia release; position and resilient" means connecting said manually operable member and element adapted to position the element to' close the exhaust valveand open the inletvalve whenthe manually operable member is in release position, of means for controlling the supply of fluid pressure toJsaid self-lapping valve mechanism including auxiliary inlet and exhaust valves, means controlled by movement of the manually operable member for-clOsing the auxiliary exhaust valve ancLmaintaining the auxiliary'inlet valve in open position to supply fluid pressure to said inlet chamber-whenever said manually operable member is moved from release position; and means for permitting theexhaust oijfluidxpressure from the outlet chamber through the auxiliary exhaust valve when the manuallyopera blemember is in release position. i

The combination with a self-lapping valve mechanism including. inlet and exhaust valves, inlet and outlet chambers, an'element Ior oper-- ating the valves, means including a member re-1 sponsive. to the pressure in the outlet chamber; for, moving the element in'one 'directiongiandmeans for moving the element intheother'ldi rection including a manually operable member having. a release position and resilient means connecting said manually operable member andelement'adapted to position the element to close the exhaust valve and open the inlet valve when: the manually operable member is in release' posia tion, of means for controlling the supply offluid pressure, to said self-lapping valve mechanism outlet chamber through said passage when the auxiliary inlet valve is open. 1 g V 6. In a self-lapping valve mechanism of the type having inlet and outlet chambers, inlet and; exhaust valves; and means for operating said valves to control the flow of fluid pressure between said chambers and to control the release of fluid pressure from the outlet chamber ili-" cluding a member responsive to the pressure-iii; the outlet chamber "for operating the valves-in one direction, a resilient member for-operating the valves in the other direction, and an operators control element having a release position and movable to operate the resilient member, means for controlling the supply of fluid pressure to the valve mechanism including auxiliary inlet and exhaust valves, and means controlled by movement of said element for operating said auxiliary valves to supply fluid pressure to the outlet chamber through the inlet chamber when the element is moved from release position and to exhaust fluid pressure from the outlet chamber when the element is in release position.

7. Control valve mechanism for controlling the supply of fluid pressurefrom a source to an actuator and for controlling the release of fluid from the actuator including a casing having an inlet chamber, an outlet chamber connected with the actuator, inlet and exhaust valves operable for respectively controlling the flow of fluid between said chambers and for exhausting fluid from the outlet chamber, means including resilient means for operating the valves, said resilient means being adjusted to normally maintain the exhaust valve in closed position and the inlet valve in open position, means responsive to the pressure in the outlet chamber for controlling the operation of the valves by said resilient means, an operators control member for the resilient means having a release position, an auxiliary inlet chamber connected with the source, an auxiliary outlet chamber connected with the first named inlet chamber, a passage between the auxiliary outlet chamber and the first named outlet chamber, a valve in said passage for permitting the flow of fluid from the first named outlet chamber to the auxiliary outlet chamber and for preventing the flow of fluid in the reverse direction, auxiliary inlet and exhaust valves for respectively controlling the flow of fluid between the auxiliary inlet and outlet chambers and the exhaust of fluid from the auxiliary outlet chamber, and means operable on movement of the operators control member for closin the auxiliary exhaust valve and maintaining the auxiliary inlet valve in open position except when the operators control member is in release position.

8. Control valve mechanism for controlling the supply of fluid pressure from a source to an actuator and for controlling the release of fluid from the actuator including a casing having an inlet chamber, an outlet chamber connected with the actuator, inlet and exhaust valves operable for respectively controlling the flow of fluid between said chambers and for exhausting fluid from the outlet chamber, means including resilient means for operating the valves, said resilient means being adjusted to normally maintain the exhaust valve in closed position and the inlet valve in open position, means responsive to the pressure in the outlet chamber for controlling the operation of the valves by said resilient means, an operators control member for the resilient means having a release position, an auxiliary inlet chamber connected with the source, an auxiliary outlet chamber connected with the first named inlet chamber, a passage between the auxiliary outlet chamber and the first named outlet chamber, a valve in said passage for permitting the flow of fluid fromthe first named outlet chamber to the auxiliary outlet chamber and for preventing the flow of fluid in the reverse direction, auxiliary inlet and exhaust valves for respectively controlling the flow of fluid between the auxiliary inlet and outlet chambers and the exhaust of fluid from the auxiliary outlet chamber, and

means including a quick lift cam operable on initial movement of the operators control member from release position to close the auxiliary exhaust valve and open the auxiliary inlet valve and operable during further movement of said operator control member to maintain said last named valve in open position.

9. Control valve mechanism for controlling the flow of fluid pressure between a source and an actuator and between the actuator and atmosphere including a casing having inlet and outlet chambers, inlet and atmospheric valves operable for respectively controlling communication between the chambers and communication between the outlet chamber and atmosphere, means including resilient means for operating said valves to normally maintain the exhaust valve in closed position and the inlet valve in open position, means responsive to the pressure of fluid in the outlet chamber for controlling the operation of the valves by said resilient means, an operators control member for operating said resilient means having a release position, an auxiliary inlet chamber connected with the source, an auxiliary outlet chamber connected with the first named inlet chamber, a passage between the auxiliary outlet chamber and the first name-d outlet chamber, auxiliary inlet and atmospheric valves for respectively controlling communication between the auxiliary inlet and outlet chambers and between the auxiliary outlet chamber and atmosphere, means operable on movement of said operators control member for closing the auxiliary atmospheric valve and opening the auxiliary inlet valve except when said control member is in release position, and means associated with said passage for permitting communication between the first named and auxiliary outlet chambers in one direction and for preventing communication therebetween in the opposite direction.

10. In a fluid pressure control system having a source of fluid pressure and an actuator, means for controlling the pressure of fluid in the actuator including self-lapping valve mechanism having an outlet chamber connected with the actuator, an inlet chamber, inlet and exhaust valves,

and means for controlling the operation of said valves including an operators control member having a release position and resilient means for connecting said member and valves and for normally maintaining the inlet valve in open position, and auxiliary valve means operable on initial movement of the control member from release position to connect said source and inlet chamber and operable when aid control member is in release position to connect said actuator with atmosphere.

1 In a fluid pressure control system having a source of fluid pressure and an actuator, means for controlling the pressure of fluid in said actuator including self-lapping valve mechanism having an outlet chamber connected with the actuator, an inlet chamber, inlet and exhaust valves for controlling the flow of fluid through said chambers, and means for controlling the operation of said valves including an operators control member having a release position and means including a resilient element for connecting said member ad valves, and means including auxiliary valve means controlled by said member operable to exhaust fluid from said actuator when the member is in release position and operable to connect said source and inlet chamber when the member is moved from said release position.

WILFRED A. EATON, 

